This invention pertains generally to glow bulbs which are conventionally used as starting devices for gas discharge lamps. More specifically, this invention pertains to techniques for electrically, thermally, and mechanically insulating a glow bulb starter from the ballast and other components associated with a gas discharge lamp. In particular, methods of manufacturing starter assemblies and ballasts are taught. U.S. patent application Ser. No. 08/686,661, filed Jul. 26, 1996, entitled "Enclosure For Glow Bulb Starter Used With Gas Discharge Lamps" by Sanders, et al., which more fully describes a device for carrying out embodiments of the present invention, is hereby incorporated by reference.
Fluorescent lamps provide illumination by generating an electrical arc and radiation inside a lamp tube. The radiation activates a fluorescent coating applied to the inner surface of the tube. To produce the arc and radiation inside the tube, a voltage is applied to the electrodes of the lamp at sufficiently high levels to generate an arc across electrodes. However, conventional fluorescent lamps must be "started" by ionizing the gas within the lamp so that the breakdown voltage needed to initiate the arc between the electrodes is reduced to a reasonably low level.
To provide the starting voltage and to control the current to the lamp, a ballast is used. In many low wattage fluorescent lamps, a magnetic ballast is used in conjunction with a glow bulb starter. The ballast limits the current to the lamp while the glow bulb starter creates an arc-inducing voltage spike across the lamp after pre-heating the lamp electrodes. Generally, the glow bulb starting device is mounted internal to the ballast enclosure. This presents a number of problems with the integrity, cost, and reliability of the ballast assembly, both in manufacturing and in operation.
First, some level of electrical isolation must be provided between the glow bulb and the other components of the ballast. Second, the glow bulb must be protected from thermal shock caused when potting compound is poured at high temperature into the ballast enclosure. Third, a secure and relatively efficient means must be used to electrically connect the leads on the glow bulb to power supply leads inside the ballast enclosure.
Several thermal and electrical isolation techniques have been used in the prior art but with limited success. Some manufacturers isolate the glow bulb lead wires from each other by covering them with dielectric tubing and tape and then wrapping the entire glow bulb and glow bulb lead assembly in Mylar tape. Other manufacturers use a paper insulation material to isolate the glow bulb from the other components in the ballast. In either case, the wrapping of the glow bulb with tape or other material is highly labor intensive and does not provide a high level of mechanical or thermal protection for the glow bulb itself. Accordingly, the glow bulbs which are installed and protected using prior art techniques are prone to failure due to thermal effects or mechanical shock.
What is needed, then, is a device for electrically insulating glow bulb leads from each other and from the other internal components of a ballast, which provides a high level of thermal and mechanical protection to the glow bulb, and which reduces the cost of installing and assembling the glow bulb within the lamp ballast enclosure. This device is presently lacking in the prior art.